Oil Production from the Bakken Formation: a Short History by Julie Lefever
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Oil Production from the Bakken Formation: A Short History By Julie LeFever Once again the Bakken Formation is in the news as oil Plays of the Bakken Formation prices rise. Over the years the State of North Dakota has Pre-1987 seen several episodes of drilling to try to recover a portion of the immense amount of oil that this formation has generated. Early exploration for Bakken oil was by conventional Beginning with the initial discovery in 1953, the Bakken has vertical drilling and began with the discovery of Antelope been a significant contributor to the North Dakota economy. Field (Fig. 1B). Oil was recovered in Antelope Field from the Over 44 million barrels of oil have been produced from this Bakken Formation in 1953 when an unsuccessful Madison formation, and there is a large potential to add to that total test (Stanolind Oil – #1 Woodrow Starr (SWSE Sec. 21, with the current oil play. T152N, R94W)) recovered oil on a drill stem test. The well was completed for 536 barrels of oil (BO) and essentially no Although a significant quantity of oil has been produced water. Offsets to this well were disappointing, so further from the Bakken it is only a fraction of what the Bakken is development did not occur until 1956 when Northern Pump capable of producing. Long considered to be a premier source Co. drilled and completed the #1 Ella Many Ribs for 320 rock, science places the oil potential of the Bakken between barrels of oil per day (BOPD). The majority of the wells for 10 and 400 billion barrels of oil (L.C. Price, pers. commun.). the field were drilled in the 1950’s and 60’s. During the A comparison of the past drilling activity in the Bakken 1980’s, renewed interest in the Antelope structure resulted Formation with the current play provides a new insight into in the drilling and completion of a number of wells along the how technology can potentially unlock oil from this virtually southern end of the feature. untapped resource. Wells were completed in Antelope Field in both the Bakken Formation and underlying thin, highly burrowed porous silty sandstone referred to as the “Sanish Sand”. Early wells in the field were drilled with a salt-based mud system; this was later changed to an oil-based mud system to prevent dissolution and the resulting casing collapse of the overlying Madison salt section. Typical completion methods consisted of perforating the well followed by a sand-oil fracture stimulation treatment. The prominent occurrence of natural fractures along the structure enhanced the production. The field has been highly successful. Fifty-two wells produce or have produced along the structure with an average initial production (IP) of 209 BO. The field produced 67,798 BO in 2003 and has a cumulative total in excess of 12.5 million barrels of oil and 10 billion cubic feet (BCF) of gas. After the development of Antelope Field, exploration of the Bakken proceeded slowly. The tight, impermeable reservoir of the Bakken required Figure 1. – A) Location map of the Williston basin. B) Fields with production from the Bakken Formation along the Nesson anticline. C) Fields producing from the Bakken along the “Bakken Fairway”. D) North Dakota fields with Bakken production adjacent to Richland County, Montana. Vol. 32, No. 1 NDGS Newsletter Page 1 natural fractures in order to produce. The next discovery in Successful wells were also drilled with oil-based fluids. the formation did not occur until 1961 when Shell Oil The Bakken shale is an oil-wet reservoir and wells that had Company used seismic methods to discover Elkhorn Ranch water introduced to the system had difficulty unloading the Field along the depositional limit in what is now known as water. Introduction of water into the system could be through the “Bakken Fairway” (Fig. 1C). drilling fluids, acidizing, or fracture stimulation methods. Acidizing Bakken wells also creates additional problems, as This was a typical Williston basin discovery. The well the treatment may react with the pyrite present in the shales was an Ordovician Red River test that recovered oil on a drill forming an iron hydroxide precipitate. stem test in the Bakken. The Shell Oil Company - #41X-5-1 Government (NENE Sec. 5, T143N, R101W) was The long history of vertically drilling the Bakken set the subsequently completed and tested 136 BOPD and a trace stage for horizontal drilling. Vertical drilling established that of water. However, the well was located in a remote area the wells with significant vertical production were draining and was often shut-in during inclement weather. It produced fractured reservoirs. It also helped to determine the proper an average of 50 BOPD until 1964, when its casing collapsed methods necessary to successfully complete a Bakken well. and the well was plugged and abandoned. Further The production decline curves display a characteristic rapid development of the Bakken did not occur in this area until drop in production over the first year, followed by steady 1976. production with virtually no decline. Another notable discovery at this time was along the Post-1987 Nesson anticline. The #1 B.E. Hove (SWNW Sec. 2, T154N, R95W) was drilled by Pan American Petroleum Corporation Drilling activity along the “Bakken Fairway” changed in Hofflund Field. During its initial test, the well flowed 756 greatly after Meridian Oil, Inc. drilled and completed the first BOPD and 3 barrels of water per day (BWPD). This well horizontal well in the Bakken Formation. The #33-11 MOI, was perforated and then treated with 10,000 gallons of acid. was initially drilled vertically. It was cored, logged, and drill Production problems resulted in two workovers with stem tested, all of which indicated that the formation was additional acid treatments followed by a water-based fracture tight. Meridian then backed up the hole and kicked off at stimulation. The well produced for two years with a 9,782 ft. Horizontal drilling was attained at 10,737 ft cumulative production of 62,700 BO. It was plugged in 1969 (measured depth) with a resulting radius of 630 ft. The well due to non-commercial production and collapsed casing. was completed on September 25, 1987 for 258 BOPD and 299 thousand cubic feet (MCF) of gas. The well had a Continued exploration for Bakken oil occurred along horizontal displacement of 2,603 ft and is now producing in the “Bakken Fairway”. Wells along the “Bakken Fairway” the upper Bakken shale that is 8 ft thick. The decline curve are not limited to Bakken production. Most of the fields have for the #33-11 was remarkably stable for the first two years multiple pays that are associated with structural features until additional nearby wells came online. The well has such as folds, faults, or both. These features contribute to produced 357,671 BO and 6,381 barrels of water (BW) the fracturing of the Bakken and may enhance the quality of through December 2003. the reservoir. The ability to produce from other formations makes it much more cost effective. The drilling activity in The success of this well set off the previous notable play this area began in the late 1970’s. dealing with the upper Bakken shale. Operators were eager to use horizontal well technology to encounter more fractures In the “Bakken Fairway”, the formation exhibits an on- and thus produce more Bakken oil. As in any play, there was lapping relationship. The stratigraphy of this area is relatively a learning curve. The #33-11 MOI took 57 days to drill and simple. The Three Forks Formation is overlain by the complete; 27 days to drill the vertical borehole and 12 days remaining, stratigraphically higher, members of the Bakken. to drill the horizontal section at a cost of $2 million. The The Bakken, in turn, is overlain by the carbonates of the third set of ten wells drilled by Meridian, further down the Lodgepole Formation. As the Bakken thins, it becomes much learning curve, had an average cost of $1.08 million and took more susceptible to fracturing and, as shown by previous 35 days to drill. By the end of the play, Meridian Oil, Inc. was drilling, fracturing is necessary for production. touting the fact that they could drill and complete a horizontal Bakken well for essentially the same price as the drilling and Successful wells were those that encountered natural completion of a vertical well, around $900,000. Successful fractures. Less than successful wells, those not encountering wells were capable of producing high volumes of oil (IP’s in natural fractures, were perforated in the Bakken shale and excess of 1900 BOPD). produced for a while. Oil was collected or diesel was substituted for produced oil and used as part of a sand/oil The play continued into the early 90’s. During the play, fracture stimulation treatment. This treatment was necessary 22 operators drilled horizontal wells. Half of these operators for economic reserves. were involved in one or two well programs. The early horizontal wells were medium-radius wells with one 2500 Page 2 NDGS Newsletter Vol. 32, No. 1 to 3500 ft horizontal leg. They were drilled underbalanced successively higher member within the Bakken has a greater or slightly underbalanced with an inverted mud system and distribution than the preceding member. The members completed with slotted liners tied back to casing. It was not eventually pinch out against the Three Forks Formation in uncommon to be stuck in the hole extending the drilling time southern Richland County. In the main play area, only the and the expense of the hole.